1. Field of the Invention
The present invention relates to an electric rotary machine suitable for high power and high speed operation, and more particularly relates to a starter for an internal combustion engine.
2. Description of Related Art
U.S. Pat. No. 5,130,596, which corresponds to Japanese Unexamined Patent Publication Hei 2-241346, discloses a rotary electric machine which has an upper coil of a single turn and a lower coil of a single turn in each slot of an armature of the armature core are extended from the armature core to have a reduced outside diameter of the extended upper coils so as to form a cylindrical commutator held by resinous material, on which brushes are disposed in contact therewith.
However, since the commutator of the above electric machine has to hold the extended upper and lower coils against centrifugal force and thermal stress, it is difficult to keep the commutating surface smooth when the machine is used as a high power machine or high speed machine.